What is istanbul?
"Yet another JS code coverage tool that computes statement, line, function and branch coverage with module loader hooks to transparently add coverage when running tests. Supports all JS coverage use cases including unit tests, server side functional tests "
istanbul is used to facilitate high-performance Node.js workflows. It provides a slim footprint of 0 KB on disk.
Installation Guide
# Install via NPM
npm install istanbul
# Install via Yarn
yarn add istanbul